GovHack 2015

WOfS Australian coverage, showing thesummary of how often water has beenobserved by Landsat satellites since 1987

Geoscience Australia is one of a number of Australian Government agencies sponsoring GovHack. Geoscience Australia will be offering datasets and sponsoring a prize for the best Science Hack - using government data for great scientific outcomes and helping people engage in, understand and use scientific information in their everyday lives.

As the national geoscientific agency, Geoscience Australia provides stewardship of a vast range of data that supports decision making in the management of Australia's precious water resources, hazard modelling for safer communities; and exploration for mineral and petroleum resources.

Contacts during GovHack

Landsat 5 and 7 Imagery dataset

Agency/Dept

Geoscience Australia

Data Set Title

Landsat 5 and 7 surface reflectance archive

Description

The Landsat satellites have provided imagery over Australia since the early 1970s. This provides an archive of data that is useful for understanding changes in the environment, agriculture, water resources and many other fields of interest. The datasets acquired by Landsat 5 (1987-2011) and Landsat 7 (1999-present) have been standardised to a systematic level to enable consistent analyses of the land surface both spatially and temporally.

The following are examples of how application of time based analysis of Landsat data can provide significant value:

Forestry and natural resource management - analysis of deforestation

Agriculture - analysis of change in soil and crop condition

Water and drought/flood management - analysis of change in water cover

City and population planning - analysis of urban and city growth

File Format(s)

The Landsat data has been processed to the Australian Reflectance Grid 25 (ARG25) specification, comprising six spectral bands at a nominal resolution of 25m.

The WMS services provide geo-referenced map images of the Landsat scenes. The WCS services provide access to the full resolution data.

The published services adhere to the following conventions:

Each scene is published as a single WMS and WCS service;

Each service consists of six layers (one layer for each band); and

The WMS services have an additional 7th layer which is a false colour composite (ie. combination of Bands 7, 4 and 1)

Landsat ARG25 is comprised of approximately 184,000 Landsat 5 and Landsat 7 scenes covering the Australian land mass and accessible as Open Geospatial Consortium (OGC) web map services (WMS) and web coverage services (WCS).

Temporal Coverage

Landsat scenes in this collection were acquired between 1987 and 2013.

Sentinel HotSpot Data dataset

Agency/Dept

Geoscience Australia

Data Set Title

Sentinel Hotspots

Description

Sentinel is a national bushfire monitoring system that provides timely information about hotspots to emergency service managers across Australia. The mapping system allows users to identify fire locations with a potential risk to communities and property. Sentinel hotspots are point data, derived from (a growing number of) satellite-born instruments that detect light in the thermal wavelengths. Typically, the satellite data are processed with a specific algorithm that highlights areas with an unusually high temperature. Sentinel Hotspots provides an important and consistent overview for management of fires across the country. The system was developed in the mid-2000 through a collaborative effort between Geoscience Australia, Australian Geospatial-Intelligence Organisation and CSIRO Land and Water. The system monitors hotspots nationally and provides timely hotspots information to its end-users. Sentinel has been a valuable input into the tools used by government and private agencies managing fires in Australia. A number of land management and emergency response agencies have taken data feeds from the Sentinel system to imbed into their routine fire management operations enhancing their situational awareness programs to assist staff, managers and the community. Hotspots data when merged with other spatial information provide a strategic picture to land managers; which allows them to understand the implications of a particular fire as well as to target resources.

File Format(s)

There are different ways and formats to access and visualise the hotspot product: 1. OGC WEB SERVICES - Sentinel allows data to be accessed via OGC Web Map Service (WMS) - which allow data to be accessed as image formats such as PNG, JPEG, and so on; and Web Feature Service (WFS) services - which allow data to be accessed as 'feature' (text records). 2. Geoscience Australia FTP Server - This contains a rolling 'last 10 days' of the hotspots in text file format. The data is 'grouped' by satellite pass; there are 2 files for each satellite pass - the hotspots themselves (in CSV format) plus a metadata file containing some information about the satellite pass from which the hotspots were identified. 3. User Interface - It is an online visualization and download tool to displays hotspots and other contextual information. There are two versions of the Sentinel UI: 'Public', which is accessible to the general public and 'Secure', which is accessible via a secure login. The Secure UI is primarily used by Emergency Management and contains hotspots produced by 'others'.

Water Observations from Space (WOfS) dataset

Agency/Dept

Geoscience Australia

Data Set Title

Water Observations from Space (WOfS)

Description

Water Observations from Space (WOfS) is a 25-m resolution gridded dataset indicating areas where surface water has been observed over time using the Geoscience Australia (GA) Earth observation satellite image data holdings. The WOfS product Version 1.5 includes observations taken between 1987 and 2014 (inclusive) from the Landsat 5 and 7 satellites. WOfS covers all of mainland Australia and Tasmania but excludes off-shore Territories.

Each satellite image pixel is an observation; successful observations are those in which the Earth's surface is clearly seen (unobscured by clouds for example) and quality checks are passed. Water is detected from these observations using an automated flood mapping algorithm created by Geoscience Australia.

The water detected for each location is summed through time and then compared to the number of clear observations of that location (i.e. observations not affected by cloud, shadow or other quality issues). The result is a percentage value of the number of times water was observed at the location. This provides relatively seamless historical water coverage for Australia, as observed by satellite. The values in the summary layer indicate how often water was observed (as a proportion of the total number of clear observations) in each cell of a 25 metre by 25 metre grid across Australia since 1987. Possible floods appear in the low values while consistent water bodies such as lakes and dams have high values.

1. A tiled dataset of the water classification results derived from each satellite observation in the Landsatarchive since 1987. Each tile is populated with values that indicate the pixel classification, viz: - Water is present - Water is absent (surface observation) - Water is undetectable (cloud/cloud shadow/pixel saturated/no data/terrain shadow/high slope) - Pixel is located in the sea

2. A cumulative statistical 'summary' dataset that combines all water observations from the entire time series into 5 tiled layers.: - ClearObservations: the total number of clear observations for the cell (pixel); - WaterObservatons: the number of times that surface water is detected for the cell; - WaterSummary: the ratio of the number of water observation to the number of clear observations; - Confidence:The Confidence Level assigned to each water observation is based on a statistical analysis of factors, including topographic position, elevation and slope, other independent satellite observations of water, topographic maps of water features, and the observation frequency. The confidence layer can be used to filter uncertain observations, for instance when displaying the data. - WaterSummaryFiltered: the Water Summary filtered to only show results where the Confidence is 1% or greater.

WOfS can be used to map and characterise inland water bodies and provides information about the observed extent of inundation for waterways and floodplains. It is a resource for both users and providers of information about surface water permanence and the extent and frequency of inundation. Potential users include government agencies, research institutions, the general public and academia.

WOfS is limited by the frequency and number of successful observations, which are determined by the satellite revisit rate (see table below) and by clouds. In particular, short-lived inundation events may not have been observed. Areas of inland Australia have been observed over 800 times, whereas highly-cloud-prone coastal and mountainous areas may have very few successful observations.

WOfS is also limited by the quality of the sensors, including their spatial resolution, and the accuracy of the water detection algorithms used. As a consequence of these limitations the product will potentially not detect the flood peak, thereby failing to capture the maximum extent of flooding. This particularly affects rapidly draining coastal catchments where the flood peak often passes before a cloud free observation is acquired.

The latest 2 versions of WOfS can be accessed via http and web services (for the summary layers). Versions are denoted as Current (latest version) and Previous (previous version) and are updated with the latest available data on a quarterly basis.

Individual water extents (dataset 1): dap.nci.org.au Data is located in the directory tree under Water Observations from Space